Modification of the ³He Phase Diagram by Anisotropic Disorder.

Motivated by the recent prediction that uniaxially compressed aerogel can stabilize the anisotropic A phase over the isotropic B phase, we measure the pressure dependent superfluid fraction of ³He entrained in 10% axially compressed, 98% porous aerogel. We observe that a broad region of the temperaturepressure phase diagram is occupied by the metastable A phase. The reappearance of the A phase on warming from the B phase, before superfluidity is extinguished at Tc, is in contrast to its absence in uncompressed aerogel. The phase diagram is modified from that of pure ³He, with the disappearance of the polycritical point (PCP) and the appearance of a region of A phase extending below the PCP of bulk ³He, even in zero applied magnetic field. The expected alignment of the A phase texture by compression is not observed. [ABSTRACT FROM AUTHOR]